1. Field of the Invention
The present invention relates generally to wireless communications and, more specifically, the present invention relates to optical communications systems.
2. Background Information
With the increasing popularity of wide area networks (WANs), such as the Internet and/or the World Wide Web, network growth and traffic has exploded in recent years. Network users continue to demand faster networks and more access for both businesses and consumers. As network demands continue to increase, existing network infrastructures and technologies are reaching their limits.
An alternative to present day hardwired or fiber network solutions is the use of wireless optical communications. Wireless optical communications utilize point-to-point communications through free space and therefore do not require the routing of cables or fibers between locations. Thus, wireless optical communications are also known as free space or atmospheric optical communications. For instance, in a free space optical communication system, a beam of light is directed through free space from a transmitter at a first location to a receiver at a second location. Data or information is encoded into the beam of light, and therefore, the information is transmitted through free space from the first location to the second location.
An important aspect of a free space optical communications system is tracking. In particular, it is important that the optical communications beam (e.g. laser beam) is aimed properly from the transmitter at the first location and that the receiver at the second location is aligned properly to receive the optical communications beam. For example, assume that a transmitter is mounted on a first building and that a receiver is mounted on a different second building. Assume further that there is a line of sight between the transmitter and receiver. It is important for the transmitter on the first building to be configured to accurately direct or aim the optical communications beam at the receiver on the second building.
Tracking is utilized for maintaining the alignment of the optical communications beam between the transmitter and receiver in various situations or disturbances. Examples of these various situations or disturbances include the swaying of the buildings due to for example windy conditions, vibration of the platforms on which the transmitter and/or receiver are mounted, atmosphere-induced beam steering, etc. If the tracking system is unable to compensate for disturbances, the optical communications beam is no longer properly aimed at the receiver and, consequently, communications between the transmitter and receiver are lost or impaired.
An apparatus is disclosed in which an optical detector is optically coupled to receive an optical communications beam directed from optics. In one embodiment, an amplifier alternating current (AC) coupled to the optical detector. A mixer circuit is coupled to receive an output of the amplifier and a communications signal. The communications signal is generated by a communications receiver circuit in response to the optical communications beam. The mixer circuit coupled to generate a first single polarity output signal in response to an output of the amplifier and the communications signal to facilitate aligned reception of the optical communications beam by the optics. Additional features and benefits of the present invention will become apparent from the detailed description, figures and claims set forth below.